Two-stroke cycle engine



Dec. 8, 1959 D. s. SANBORN 2,916,023

' TWO-STROKE CYCLE ENGINE Filed May 9, 1957 3 Sheets-Sheet l DA/WEL $2.SANBORM INVENTOR.

A l/orney Dec. 8, 1959 D. s. SANBORN 2,916,023

TWO-STROKE CYCLE ENGINE Filed May 9, 1957 3 Sheets-Sheet 2 DAN/E L 5.SANBOR/V,

INVENTOR.

' Ai /army United States Patent TWO-STROKE CYCLE ENGINE Daniel S.Sanborn, San Diego, Calif., assignor to McCulloch Motors Corporation,Los Angeles, Calif., a corporation of Wisconsin Application May 9, 1957,Serial No. 658,134

3 Claims. (Cl. 123-32) This invention relates to spark-ignition,fuel-injection, two-stroke cycle engines and relates in particular to anengine and a method of operating the same so as to achieve greaterefficiency, and smooth, steady power output over the entire speed andload range of the engine. This application is a continuation-in-part ofmy copending application, Serial No. 417,286, filed March 18, 1954, forEngine.

It is an object of the invention to provide an engine of this characterhaving improved means for the injection of the fuel in a manner toaccomplish a more efiicient combustion of the fuel-air mixture.

It is another object of the invention to provide a novel spark-ignition,fuel-injection, two-stroke cycle engine in which fuel is injected intothe moving fresh air mass within the cylinder at such a time that anapproximately stoichiometric fuel-air mixture is formed moving towardthe point of spark-ignition, thereby producing an easily ignitablemixture local to the point of spark-ignition when the piston in thecylinder has reached approximately top dead center position, over theentire speed and load range of the engine.

It is another object of the invention to provide a novel method foroperating a spark-ignition, fuel-injection, two-stroke cycle engine inwhich air under pressure is introduced into the engine cylinder in amanner to produce a moving air mass rising upwardly in the cylindertoward the spark-ignition point in the upper end thereof and in which atpart load a quantity of fuel corresponding to the reduced loadrequirements of the engine is injected into the moving air mass in adownward direction to produce a non-uniform fuel-air mixturecharacterized by the formation of a locally ignitable mixture within theair mass moving upwardly toward the sparkignition point.

It is a further object of the invention to provide a novel method foroperating a spark-ignition, fuel-injection, two-stroke cycle engine inwhich, for high load requirements, fuel injection is begun shortly afterbottom dead center position of the piston and is directed oppositely tothe direction of flow of the entering fresh air mass in order to obtaingood mixing and complete dispersement of the fuel air mixture within thecombustion chamber, and for light load requirements fuel injection isretarded and is directed into the less turbulent air mass duringcompression of the gases in order to obtain a stratified fuel-airmixture ignitable in the region of the combustion chamber local to thespark plug electrodes.

It is a further object of the invention to provide a method and meansfor introducing the injected fuel either liquid, vapor or gas, into thecylinder in the form of a filled cone so the fuel will be distributedwith greater uniformity in the selected area of the cylinder whichvaries in magnitude with load conditions.

It is a further object of the invention to provide an engine of thecharacter described having means for producing a conical and distributedinjection of the fluid 2,916,023 Patented Dec. 8, 1959 fuel cooperatingwith other parts so as to produce the improved action herein set forth.

Further objects and advantages of the invention may be brought out inthe following part of the specification wherein some details have beendescribed for the purpose of amplifying the disclosure, withoutintending, however, to limit the scope of the invention which is set'forth in the appended claims.

Referring to the accompanying drawings which are for illustrativepurposes only:

Fig. 1 is a sectional view showing my invention embodied in a singlecylinder engine;

Fig. 2 is a fragmentary cross-sectional view taken substantially asindicated by the line 22 in Fig. 1 and showing approximately theinjection of fuel under full load operation;

Fig. 3 is a view showing the cylinder and the piston positioned at thetime of fuel injection for reduced power output of the engine;

Fig. 4 is a view similar to Fig. 3, but showing the position of thepiston in the cylinder at the time of fuel injection for operation ofthe engine under idling conditions;

Fig. 5 is a cross section taken substantially as indi cated by the line55 of Fig. 2;

Fig. 6 is an enlarged cross-sectional view taken as indicated by theline 6-6 of Fig. 1;

Fig. 7 is an enlarged sectional view of the fuel injector means forminga part of the invention; and

Fig. 8 is an enlarged fragmentary sectional view schematicallyindicating the manner in which the conical injection spray is produced.

The engine E, as shown in Fig. 1, includes a cylinder 10, a piston 11, acrankshaft 12 and a connecting rod 13 for connecting the piston with thecrankshaft. Being of two-stroke cycle type the cylinder has exhaustports 14 and their inlet ports 15 positioned so as to be uncovered bythe piston 11 when it reaches the lower end of its movement in thecylinder 10.

A centrifugal compressor 16 is provided for feeding air under pressurethrough a duct 17 to passages 18 in the engine which communicate withthe air inlet ports 15. This air compressor 16 is driven from thecrankshaft 12 through a variable speed V-belt drive 19 including avariable diameter sheave 20 mounted on the crankshaft 12, a V-belt 21,and a driven sheave 22 which is mounted on a shaft 23 which is connectedto the impeller 24 of the compressor 16.

As shown in Fig. 2, the upper end wall 24 of the cylinder 10 has adownwardly faced recess 25 for the fuel injection and ignition equipmentof the engine. The recess 25 is located on the side of the engineopposite from the ports 14 and has in the upper wall 26 thereof a fuelinjection nozzle 27 disposed on a center line aa which, if projecteddownwardly, would intersect the top of the piston 11 at a point P nearits center but offset from the piston center toward the side of thecylinder opposite from the injector 27, when the piston 11 is in loweredposition. The recess 25 has a sloping wall 28 spaced from the outer wallof the cylinder 10 and therein a spark plug 29 is located and positionedso that the spark gap 30 of the spark plug 29 is located either in orclose to the cone 31 defined by the fuel which is injected by the nozzle27 downwardly and diagonally within the cylinder space 32.

As shown in Fig. 7, the injector nozzle 27 includes a body 40 having atits lower end an outwardly projecting axial abutment 41 which iscylindrical in form and has a substantially flat end face 42. The narrowperipheral portion 43 of the end face 42 constitutes an annular valveseat which may be referred to as a peripheral valve seat circumscribingthe area 44 of the end 3 face 42. A short cylindrical marginal wall 45projects downwardly from the body 40 and cooperates with the abutment 41to form an annular fuel chamber 47 in surrounding relation to theabutment 41. A circular metal plate or disc 48, originally flat, issecured across the forward or lower end of the body 40 in such a mannerthat a bending strain will be placedltherein because the' outer end ofthe abutment 41 projects further from the body 40 than the end face 49of the marginal wall 45, so that the annular seat 43 lies in a planeoutwardly offset from the plane defined by the end face 49 of themarginal wall 45, resulting in the thin plate 48 being slightly dishedwhen its peripheral portion 50 is clamped against the end face 49.

A sleeve 52 surrounds the body 14 and has a radially inwardly directedlip 53. A second body part 54 rests against the inner end of the body 48and is provided with external threads 55 onto which may be'screwed theinternal threads 56 of the sleeve 52, to cause the lip 53 to tightlyclamp the peripheral portion 50 of the plate 48 against the end face 49of the marginal wall 45. The dishing of the plate 48 in the mannerdescribed in the foregoing accomplishes a tight engagement of the plate43 with the corner 57 of the abutment 41 at the periphery of the endface 42 thereof, to give aneffective annular sealing of the chamber 47.I

A central opening 59 is provided in the plate 48, this opening exposingthe area 44 of the end face 42 circumscribed by the peripheral seat 43.The opening 59 of the plate 48 is defined by an inner circular Wallportion 60 thereof which overlaps the annular peripheral portion 43 ofthe end face 42. The bodies 40 and 54 are provided with passages 58communicating with the annular chamber 47 when the liquid fuel charge isforced under high pressure through these passages into the chamber 47,the plate 48 will be further flexed downwardly, as shown in Fig. 8, sothat the annular wall portion 60 thereof will be moved downwardly awayfrom the peripheral portion 43 of the abutment 41, leaving between theparts 43 and 60 an annular spray orifice 62 having an area which isvariable in keeping with the rate of flow or volume of the liquid fuelwhich must be discharged from the nozzle during the extremely shortinjection time in the operation of the engine. During the injection ofthe liquid fuel a thin annular sheet of the fuel passes through theorifice62, as indicated by arrows' 63 in Fig. 8, and the inwardly movingfuel is subjected to high turbulence in the small area 64 adjacent thecenter of the abutment in face 42, and the fuel is subjected to anabrupt change in its direction of flow, resulting in a conical jet ofatomized fuel particles along the axis aa as indicated by arrows '65.The injection of the fuel into the cylinder in atomized condition and soas to define a cone 31, Fig. 2, contributes importantly to the highefficiency of the engine under the varying conditions of operationencountered.

For the periodic delivery of fuel charges to the injection nozzle 17 aninjector pump 66 is provided having a plunger 67 adapted to be actuatedby a cam 68 mounted on a shaft 69 which is rotated in synchronism withthe rotation of the engine crankshaft 12, but may be retarded oradvanced as operating conditions of the engine may require. Along oneside of the cylinder there is a shaft 70 which is driven by thecrankshaft 12 through a helical gear set 71. The lower end of the shaft70 is connected to an oil pump 72 which delivers oil from the crankcaseof the engine to a system'of passages 73 for the delivery of oil todifferent parts for the lubrication thereof. The upper end of the shaft70 is connected to an ignition distributor 74 which in timed relation tothe movement of the piston '11 delivers high voltage ignition current tothe spark plug 29. A helical gear 75, mounted on the shaft 70 below thedistributor 74, drives a companion helical gear 76 which is fixed on ashaft 77 aligned with the shaft 69.

The rightward end 78 of the shaft 77 is supported in a cavity 79 whichis connected to the oil passage system 73 of the engine through apassage 80. The leftward end 81 of the shaft 77 has the hub 82 of acylinder 83 secured thereon. The rightward end 84 of the shaft 69projects into the cylinder 83, across the interior space thereof andinto the hub 82 so as to lie in confronting relation to the leftward end81 of the shaft 77. As shown in Fig. 2, the cylinder 83 has'thereinwalls 85 which lie in a plane which is parallel to or coincideswith the axis of the cylinder 83, and extend from the peripheral wall ofthe cylinder 83 to the shaft 69, thereby dividing the interior of thecylinder into two semi-cylindrical chambers 86. Vanes 87 projecteddiametrally from the portion 84 of the shaft 69 in the cylinder 83 intosliding engagement with the inner face of the circumferential wall ofthe cylinder 83, defining'in the chambers 86 compartments 88 which areadapted to receive oil under pressure from the recess 79 through oilpassages '89 and 90 respectively in the shafts 77 and 84, and radialports 91 which connect the leftward end of the passage 90 with thecompartments 88.

As viewed in Fig. 2, a plurality of small openings 92 are arranged onhelixes in the wall portions 93 of the cylinder 83. Oil fed underpressure through the ports 91 into the compartments 88 will move thevanes 87 in clockwise direction 'until the inner ends of unobstructedopenings are uncovered. Oil will then flow out through theseunobstructed openings and there will be no further clockwise rotation ofthe vanes 87. The selective'uncovering of the outer ends of the openings92, and likewise the covering or obstruction of the openings 92 isaccomplished by an outer sleeve 94 which fits around the cylinder and isaxially slidable thereon, from the position wherein the sleeve 94 closesall of the openings 92, as shown in full lines in Fig. 1, and the dottedline position 94 wherein all of the openings 92 are uncovered. If all ofthe openings 92 are uncovered, fluid pressure in the compartments 88will rotate the vanes 87 until the inner ends of the first openings 92aare uncovered sufliciently to permit escape of oil from the compartments88 as fast as the oil enters the same, the result being that the vanes87 will occupy an intermediate position as shown in Fig. 2. If thesleeve 94 is moved so as to cover the first openings 92a, then oilpressure in the compartments 88 will move the vanes further in clockwisedirection until the inner ends of unobstructed openings 92 areuncovered. Since the vanes 87 are fixed on the shaft 69 the covering anduncovering of selected openings 92 will rotate the cam 68 relatively tothe shaft 77 whereby the position of the cam 68 may be retarded oradvanced with respect to the rotation of the engine crankshaft 12.

The injector pump 66 is schematically shown in Fig. 6, since it is ofthe well known Bosch type having a barrel 96 provided with a fuel inletopening 97 which is uncovered when the plunger 67 is retracted. Rotationof the cam 68 will move the plunger 67 rightwardly from the position inwhich it is shown in full lines in Fig. 6, first closing the fuel inletport 97 and then forcing the fuel from the barrel 96 out through a fueldischarge passage '98 which communicates with the passages 58 of theinjection nozzle 27. The rotational adjustment of the cam 68 by relativemovement of the vanes 87 within the cylinder 83 makes possible theadjusting of the cam 68 to advancethe injection period when the engineis operating at high load and retard the injection period when theengine is operating under other conditions, such as reduced load andidling, for example, as required in the operation of internal combustionengines.

When the engine is operating at full load, the injection is begun at atime shortly after the piston has reached bottom dead center, .forexample, at a crank angle at about after top dead center position of thepiston, and the injection is terminated by the time the top face of thepiston has traveled to approximately the quarter way position in thecylinder 10, for example, 25 of crank angle rotation after the startingof the injection period. Injection occurs after the ports 14 and 15 havebeen uncovered so that the fresh air entering the chamber 32 through theports 15 has had an opportunity to remove the major portion of theexhaust gases through the eX- haust ports 14, and at the time fuelinjection is started, the piston is moving upwardly in the cylinder sothat the exhaust ports are closed before injected fuel can escapetherefrom. Loop scavenging is accomplished by directing the enteringfresh air in an upward direction toward the side of the cylinderopposite from the exhaust ports and toward the injection nozzle, therebyestablishing a flow of air and exhaust gases up one side of thecombustion chamber, across the top of the chamber, and down the oppositeside of the chamber to escape near the bottom thereof through theexhaust ports 14.

For full load operation of the engine the vaporized liquid fuel is ofsuch quantity that in order to produce rapid combustion when theignition spark passes across the spark gap of the plug 29, the atomizedfluid must be evenly dispersed throughout the cylinder space.

At part load operation, the timing of the fuel injection is delayed inorder to limit the diffusion of the hydrocarbon vapors laterally withinthe combustion chamber 32. In this way, the hydrocarbon-air proportionsexposed to the ignition spark are such that good combustion will beaccomplished; whereas, either too high a concentration of hydrocarbonelements at the spark gap or too great dispersion of the hydrocarbonvapors in the cylinder space 32 will result in poor response to ignitionas explained. 'When the engine is operating under full load conditionsfuel injection will start after the piston has started upwardly from thebottom center position in which it is shown in Fig. 2 and will terminatewhen the upper face of the piston 11 reaches a position, such asindicated by the broken line bb. The conical spray of atomized fuel hasan area at its lower end which is substantially the same as the area ofthe cylinder above the ports 14 and 15, and therefore, the fuelparticles are dispersed over a large area corresponding to the area ofthe upper end of the piston 11 and as the piston 11 continues its upwardmovement toward top center position hydrocarbon fuel will be quiteevenly dispersed across the area of the combustion chamber and a readilyignitable fuel-air mixture will be presented to the ignition spark whichappears across the gap 30. Under intermediate load, ignition may startwhen the piston 11 has reached an intermediate position, such as shownin Fig. 3. At this time the area of the injection cone 31, where itintercepts the upper face of the piston 11, will have a smaller diameterd. The injection cycle which has started when the piston 11 is in theposition in which it is shown in Fig. 3 will be discontinued when theupper face of the piston 11 reaches the position indicated by the brokenline ee. The dispersal of the hydrocarbons laterally within the cylinderspace 32 will be diminished to such an extent that when the pistonreaches a position close to top dead center, or ignition position, astoichiometric fuel-air mixture will be presented to the spark createdat the spark gap 30.

Under minimum conditions of power delivery by the engine, injection ofthe fuel charge into the cylinder will not start until the piston 11reaches the position in which it is shown in Fig. 4, and the injectionof fuel will terminate shortly thereafter, or when the upper face of thepiston 11 reaches the position indicated by the line ff. The area of theinjection cone 31, where it intercepts the upper face of the piston 11,will have a smaller diameter d. There will be a minimum lateraldispersal of the small amount of hydrocarbon fuel injected due toreduced mixing time and air motion, and the fuel air proportionspresented to the ignition spark when the piston 11 reaches approximatelydead center will be of such proportions as to be readily ignited by thespark.

To accomplish the timing and duration of the injection periods theplunger 67 of the injection pump 66 has, in operative relation to theinlet port 97 a spiral cutoff shoulder 100 and a circular pressurerelease shoulder 101. Viewed from the rightward end thereof, clockwiserotation of the plunger 67 from the position in which it is shown inFig. 6, will circularly move the cutoff shoulder 100 with relation tothe inlet port 97 so that the cutting off or closing of the port 97 bythe plunger 67 will be delayed proportionately to the rotation of theplunger 67. Rotation of the plunger 67 is controlled by a rotatablemember 102 which surrounds the stem 67a of the plunger 67 and hastherein a longitudinal slot 103 or keyway into which a lug 104 projectsfrom the face of the stem 67a. The rotatable member 102 has a gear 105formed thereon engaged by a rack 106 so that by movement of the rack 106by either automatic or manually operable means will effect rotation ofthe member 102 which will be transmitted through the lug 104 to theplunger 67. The details of the distributor 74 are not shown for thereason that this distributor may be of a type commonly used on internalcombustion engines, having means for advancing and retarding of the timeat which the high voltage, spark forming current is delivered to thespark plug.

I claim:

1. In a two-cycle, fuel injection, spark ignition engine: a cylinderside Wall having exhaust and air inlet ports at the lower end of thecylinder space defined by the cylinder wall; a cylinder top wall; apiston operative in said cylinder; an injector nozzle in said cylindertop wall.

characterized by delivering a conical spray of fuel downwardly into thecylinder space toward said piston, said nozzle comprising a body havingin the lower end thereof a centralized abutment, a fuel receiving spacearound said abutment, ducts for conveying the fuel from the exterior tosaid fuel receiving space, and a thin plate positioned across said lowerend of said body so as to cover said fuel receiving space, said platehaving therein a spray opening smaller in diameter than the diameter ofsaid abutment and confronting the face of said abutment whereby anannular spray orifice is formed between the end face of said abutmentand the contiguous portion of said plate, which will efiect anatomization of the fuel as it leaves said opening of said plate in theform of a cone; spark means in the top portion of said cylinder spaceadjacent said injector nozzle; and means for delivering separate chargesof fuel to said nozzle, said fuel delivery means operating in timedrelation to the movement of said piston in said cylinder and havingmeans for varying the size of said charges between minimum and maximumand for delaying the delivery of said charges to said nozzle incorrelation to the movement of said piston in said cylinder so that theinjection of said maximum charges will start when said piston is nearthe bottom of its compression stroke and the charges of progressivelydecreasing size are delayed for periods of time corresponding toprogressively upwardly spaced positions of said piston as it movesthrough tis compression stroke, to effect lateral distribution of thefuel particles of the injected fuel charges over areas in the cylinderspace varying from maximum to minimum as the sizes of said charges arevaried from maximum to minimum.

2. In a two-cycle, fuel injection, spark ignition engine: a cylinderside wall having exhaust and air inlet ports at the lower end of thecylinder space defined by the cylinder wall, said inlet port beingarranged so as to deliver air upwardly in the side portion of saidcylinder space opposite from the side of the cylinder containing saidexhaust port; a cylinder top wall; a piston operative in said cylinder;an injector nozzle in said cylinder top wall at the upper end of saidside portion of said cylinder spacecharacterized by delivering a conicalspray of fuel downwardly into the cylinder space toward said piston,said nozzle being set angularlyso that the, axis of the conical spraydelivered thereby will intersect a nearcentral point in the top of saidpiston, when it is in lowered position in the cylinder, said nozzlecomprising a body having in the lower end thereof a centralizedabutment, a fuel receiving space around said abutment, ducts forconveying the fuel from the exterior to said fuel receiving space, and athin plate positioned across said lower end of said body so as to coversaid fuel receiving space, said plate having therein a spray openingsmaller in diameter than the diameter of said abutment and confrontingthe face of said abutment whereby an annular spray orifice is formedbetween the end face of said abutment and the contiguous portion of saidplate, which will effect an atomization of the fuel as it leaves saidopening of said plate in the form of a cone; spark means in the topportion of said cylinder space adjacent said injector nozzle; and meansfor delivering separate charges of fuel to said nozzle, said fueldelivery means operating in timed relation to the movement of saidpiston in said cylinder and having means for varying the size of saidcharges between minimum and maximum and for delaying the delivery ofsaid charges to said nozzle in correlation to the movement of saidpiston in said cylinder so that the injection of said maximum chargeswill start when said piston is near the bottom of its compression strokeand the charges of progressively decreasing size are delayed for periodsof time corresponding to prog-ressively upwardly spaced positions ofsaid piston as it moves through its compression stroke, to effectlateral distribution of the fuel particles of the injected fuel chargesover areas in the cylinder space varying from maximum to minimum as thesizes of said charges are varied from maximum to minimum.

3. In a two-cycle, fuel injection, spark ignition engine: a cylinderside wall having exhaust and air inlet ports at the lower end of thecylinder space defined by the cylinder wall; a cylinder top wall; apiston operative in said cylinder; an injector nozzle in said cylindertop wall characterized'by delivering a conical spray of fuel downwardlyinto the cylinder space toward said piston, said nozzle comprising abody having in the lower end thereof a centralized abutment, a fuelreceiving space around said abutment, ducts for conveying the fuel fromthe exterior to said fuel receiving space, and a movable memberpositioned across said lower end of said body so as to ;cover said fuelreceiving'space and having therein a spray opening smaller in diameterthan the diameter of said abutment and confronting the face of saidabutment whereby an annular spray orifice is'formed between the end faceof said abutment and the contiguous portion of said movable member,which will effect an atomization of the fuel as it leaves said openingof said ment of said piston in said cylinder so that the injection ofsaid maximum charges will start when said piston is near the bottom ofits compression stroke and the charges of progressively decreasing sizeare delayed for periods of time corresponding to progressively upwardlyspaced positions ofsaid piston as it moves through its compressionstroke, to effect lateral distribution of the fuel particles of theinjected fuel charges over areas in the cylinder space varying frommaximum to minimum as the sizes of said charges are varied from maximumto minimum. V

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